Because of increasingly strict solvent emissions regulations in recent years, low solvent emission paints have become very desirable. A number of high solids paint compositions have been proposed to meet these low solvent emission requirements. However, many of these compositions are deficient because of difficulty in application, slow curing rates, complex and/or consuming composition formulation, poor durability and low solvent and water resistance of the coating.
Compositions which have been proposed to overcome these deficiencies are taught in U.S. applications Ser. Nos. 334,698, 334,800 and 334,801, filed Dec. 12, 1981 in the name of Chattha. In these compositions, branched diols react with anhydrides of dicarboxylic acids to produce hydroxy acids and polyacids. The composition of such a mixture is largely dictated by the stoichiometry of the reactants employed. These acid products can then be reacted with epoxies to produce hydroxy resins. Subsequently, a composition comprising a mixture of these hydroxy resins and amine-aldehyde crosslinking agent can be applied to a substrate and cured at elevated temperatures to obtain crosslinked structures. Unexpectedly, we have now found that all the materials use to prepare these prior compositions can be singly combined and all of the aforementioned reactions carried out in situ during curing on the substrate to obtain high solids coatings with excellent physical properties. While not wishing to be bound by theory, it is believed that in this reaction sequence the polyol reacts with the anhydride to produce acid functionality which further reacts with the epoxy to produce hydroxy moiety; then at higher temperatures, the amine-aldehyde reacts with hydroxy functionality to produce a crosslinked network. This crosslinking reaction is facilitated by the unconsumed acid present in the composition.